1. Field of the Invention
This invention relates to an apparatus for taking a copy of an image formed on a board.
2. Related Background Art
A copying apparatus has been known which is capable of producing a copy of an image written on a writing board. This type of apparatus has a printer which is used exclusively for copying the image written on the board. Thus, the printer produces only the image written on the board. This means that offices have to be equipped with another copier for the purpose of copying various original documents.
To obviate this problem, apparatuses have been proposed which have a copier capable of copying both the image written on the board and the images of original documents. Examples of such apparatus are disclosed, for example, in the specification of the U.S. Pat. No. 4,648,706 and specifications of the U.S. patent application Ser. Nos. 883,653; 921,432; 005,775; 070,193 and 075,992.
In these apparatuses, the adjustment of density of copy is adjusted by means of a density control means which is provided on the copying unit rather than on the board unit.
The writing board usually has a constant level of brightness. It is extremely difficult to operate the density control means to adjust the copy density in conformity with the level of the brightness of the writing board each time the board image is copied.
Another problem resides in that the copying operation may be fail due to any offset in the positional relationship between the image on the board and the copying unit. In such a case, the copying operation has to be suspended and restarting the copying operation requires additional work. It is highly desirable that the copying operation can be restarted without difficulty.
In the operation of the apparatus of the described type, the image written on the writing board is scanned during the copying cycle. In the event that a copying material such as paper has been accidentally jammed, the copying unit is stopped without delay. A smooth and easy restart of the apparatus is required also in this case.
Furthermore, troubles are encountered such as an accidental interruption of continuous copying operation for copying an original on the copying unit, when an instruction is given for preferentially copying a board image during the continuous copying of the original on the copying unit or when the operator has happened to operate the apparatus for copying a board image without being aware of the functioning of the copying unit in the continuous copying mode.
This type of apparatus also requires a special sequence capable of controlling the operations of the board unit and the copying unit which are constructed and mounted separately. When a long time is required for starting up a board illumination lamp, light is unnecessarily introduced to the copying unit until the board illuminating lamp starts up. In addition, it often happens that the board copying operation is stopped due to any failure in the board unit before the copying is actually commenced, while the copy paper sheets have been already fed in response to a copying instruction. In such a case, the paper jams in the copying unit, requiring a laborious work to remove the jammed paper.
The apparatus of the kind described generally employs such a routine that the illuminating lamp for illuminating the sheet on the board is started in advance of the operation for copying an image on the board and the copying operation is actually commenced after the quantity of light from the lamp has reached a level necessary for the copying operation, with the lamp turned off after completion of the process. The time until the required quantity of light is reached does not matter when the ambient air temperature is moderate. The startup of the illuminating lamp, however, is delayed when the ambient temperature is low, so that an impractically long time is wasted before the copying operation is actually commenced. A large difference in the waiting time until the copying unit becomes ready to operate, due to variation in the temperature, is irritating the user.